This invention relates to a process for the production of flame-retardant polyurethane products by mixing acid boron salt-forming compounds and basic salt-forming compound in a polyol and/or a polyisocyanate, then reacting the polyol and polyisocyanate.
The production of polyurethane products is well known in the Arts any many types of flame-retardant chemicals have been used in the process. It is also known in the Arts that salts of boric acid are useful as a flame-retardant; and require the addition of other flame-retardants therefore, they are not very useful. In the novel process of this invention, only a small amount of acid boron compounds are necessary to produce a flame-retardant product because the molecules of the boric acid are small and very well distributed throughout the product. In the process of this invention, low-cost and readily available compounds are utilized and there is an improvement in the cost of the product, in the amount of flame-retardant needed, and in the production of inexpensive flame-retardant compounds.
While not wishing to be bound by any theory of operation, it appears that there may also be some reaction of the acid boron compounds with the basic salt forming compound, the polyol or polyisocyanate to give a much better and more stable distribution of boric acid and salts, thereby proving flame-retardant properties. Any excess of basic salt-forming compounds may be used as a filler or may be or may not be a reactant in the process. It takes an amount at least 3 to 5 times more when the salt of acid boron compound is added to the reactive mixture to produce flame-retardant polyurethane products than it does when the salt is produced as outlined in this invention. The flame-retardant boric acid and salt produced by the process of this invention is less expensive and at least equal to, or better than, the commercially available flame-retardant agents for polyurethane products in flame-retardant properties.
In the production of flame-retardant polyurethane products utilizing acid boron compounds it is necessary to utilize a basic compound to adjust the pH. Boric acid is a reaction retarder and slows down the chemical reaction therefore a satisfactory foam can not be produced unless the pH is elevated to above a pH of 6, preferably to above a pH of 7. The pH is elevated by adding a basic compound to the emulsion or mixture of the components. It is preferable that the basic compound does not react with the acid boron compound but in many of the mixtures of components some reaction takes place between them. When they react together only a minimum amount of the basic compound should be used. A combination of a basic compound which does not react with the acid boron compound and a basic compound which does react with the acid boron compound may be used so that free acid boron compound may be present in the reaction mixture.